diff --git a/infection.json5 b/infection.json5
index 9426b75..57864a2 100644
--- a/infection.json5
+++ b/infection.json5
@@ -39,7 +39,9 @@
         "Coalesce": {
             "ignore": [
                 // Cannot test this case.
-                "Fidry\\CpuCoreCounter\\CpuCoreCounter::getAvailableForParallelisation"
+                "Fidry\\CpuCoreCounter\\CpuCoreCounter::getAvailableForParallelisation",
+                // Not interested in testing this case.
+                "Fidry\\CpuCoreCounter\\Finder\\ProcOpenBasedFinder::diagnose"
             ]
         },
         "Continue_": false,
diff --git a/src/Finder/CpuInfoFinder.php b/src/Finder/CpuInfoFinder.php
index dea4c41..8013877 100644
--- a/src/Finder/CpuInfoFinder.php
+++ b/src/Finder/CpuInfoFinder.php
@@ -49,10 +49,12 @@ public function diagnose(): string
         }
 
         return sprintf(
-            'Found the file "%s" with the content:%s%s',
+            'Found the file "%s" with the content:%s%s%sWill return "%s".',
             self::CPU_INFO_PATH,
             PHP_EOL,
-            $cpuInfo
+            $cpuInfo,
+            PHP_EOL,
+            self::countCpuCores($cpuInfo)
         );
     }
 
diff --git a/src/Finder/ProcOpenBasedFinder.php b/src/Finder/ProcOpenBasedFinder.php
index 793ec64..4d51f89 100644
--- a/src/Finder/ProcOpenBasedFinder.php
+++ b/src/Finder/ProcOpenBasedFinder.php
@@ -56,16 +56,19 @@ public function diagnose(): string
 
         return $failed
             ? sprintf(
-                'Executed the command "%s" which wrote the following output to the STDERR:%s%s',
+                'Executed the command "%s" which wrote the following output to the STDERR:%s%s%sWill return "null".',
                 $command,
                 PHP_EOL,
-                $stderr
+                $stderr,
+                PHP_EOL
             )
             : sprintf(
-                'Executed the command "%s" and got the following (STDOUT) output:%s%s',
+                'Executed the command "%s" and got the following (STDOUT) output:%s%s%sWill return "%s".',
                 $command,
                 PHP_EOL,
-                $stdout
+                $stdout,
+                PHP_EOL,
+                $this->countCpuCores($stdout) ?? 'null'
             );
     }
 
diff --git a/tests/Finder/ProcOpenBasedFinderTestCase.php b/tests/Finder/ProcOpenBasedFinderTestCase.php
index a0a79ba..0801708 100644
--- a/tests/Finder/ProcOpenBasedFinderTestCase.php
+++ b/tests/Finder/ProcOpenBasedFinderTestCase.php
@@ -63,8 +63,8 @@ public function test_it_can_do_a_diagnosis(
 
     public static function diagnosisProvider(): iterable
     {
-        $stdoutResultRegex = '/^Executed the command ".*" and got the following \(STDOUT\) output:\nsmth in stdout$/';
-        $stderrResultRegex = '/^Executed the command ".*" which wrote the following output to the STDERR:\nsmth in stderr$/';
+        $stdoutResultRegex = '/^Executed the command ".*" and got the following \(STDOUT\) output:\nsmth in stdout\nWill return "(null|\d)"\.$/';
+        $stderrResultRegex = '/^Executed the command ".*" which wrote the following output to the STDERR:\nsmth in stderr\nWill return "(null|\d)"\.$/';
 
         yield 'could not execute command' => [
             null,